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crossover freq settings  

post #1 of 27
Thread Starter 
Ok....
I have an Anthem AVM20, small speakers all around with a sub.....

I have the crossovers for the speakers set at 80 hz....

The setup menu then asks for a subwoofer crossover setting.......

What should this be set at ?
It can be set at 5hz increments from 20-120 hz....

Thanks

Shelly
post #2 of 27
In this plain vanilla case, the sub should also be set to 80 Hz.

Ed
post #3 of 27
Now thats a REEEL crossover. 5Hz increments...dayem.
post #4 of 27
Quote:
Originally posted by mjosef
Now thats a REEEL crossover. 5Hz increments...dayem.
You get what you pay for.

Ed
post #5 of 27
Hmmm. Why a sub crossover?
post #6 of 27
DMF,..
The sub has a lowpass crossover,..The other speakers in the system have a highpass crossover.
>>>--->
post #7 of 27
Thread Starter 
Ok....

So if I have this right,
The mains, and center, and surrounds get a signal that is cut off at about 80 hz and below, only receiving signals above 80 hz

and the sub, if I set that crossover at 80 hz also, it won't get any significant signal ABOVE 80hz....

Is this all correct ?

So setting the sub crossover at 90hz is ok,
but setting it at say, 60 would be bad, as I would be leaving a hole from 60 -80 hz....

Is that right?

One more question...while I have some attention....

I can't defeat the crossover built into the sub, so I guess I should set that as high as possible... I think it is at 120 hz.... right ?

Thanks

Shelly
post #8 of 27
Shelly40,..
Well,...yes, you have the right idea,...What hasn't been discussed,and for the most part doesn't really need to be given what we are dealing with,....is roll off. I'm not sure what the roll off of the crossover in the anthem is,...but for practical explanation,...The crossover doesn't cut off output at a specific frequency,....it starts at that level, and slowly lessens the frequencies above or below that point, depending on weather its a high-pass or low-pass crossover.
There again, yes...If you cross over your mains at say 100,..and the sub at 40, then yes, you could realize a hole, so to speak in between the two crossover points.
Again, given what you have there, all small speakers accept the sub, you could cross them all over at 80,....High-pass for the mains and surrounds, and low-pass for the sub. If you can't turn the sub crossover off, then turn it all the way up, and let the Anthem do the work.
The AVM20 is very tweekable, and will allow you to set about any system up anyway you like,...Each speaker individually if you like,....Not sure exactly what speakers you have, but you have many options with the Anthem,...Dig deep enough in that monster of a manual, and you will find, that machine will all but give you a massage while your listening to your favorite music,....;)

GRCRY,...>>>--->
post #9 of 27
Quote:
Originally posted by GRCRYSTYK
DMF,..
The sub has a lowpass crossover,..The other speakers in the system have a highpass crossover.
I understand that. The question was WHY? If you set the low pass below any of the other speakers' crossovers, you lose information. If you set it higher it has no purpose.

So I ask again. Why? :confused:
post #10 of 27
Quote:
Originally posted by DMF
I understand that. The question was WHY? If you set the low pass below any of the other speakers' crossovers, you lose information. If you set it higher it has no purpose.

So I ask again. Why? :confused:
The crossovers in receivers really are 2 filters - one high pass for the satellite speakers and the other is a low pass for the sub. The low pass is needed because the full spectrum from the "small" channels need to be low passed to be combined with the LFE channel to send to the sub (actually the full spectrum of the small channels is combined with the entire LFE channel and then the low pass filtering takes place). Most recievers have global Xovers (meaning that all small channels use the same Xover frequency) and so it is clear that both the high pass and low pass should be the same and so one only gets to choose one Xover frequency - but it applies to BOTH the high AND low pass filters. But on the Anthem, each small channel can have it's own high pass frequency. But applying the corresponding low pass for each channel would really mess things up because a filter also has phase response in addition to amplitude response. When combining all the different low passed signals with different phase responses, you'd have a very irregualar bass response. The easy solution is to choose a single low pass frequency for all small channels, regardless of what the high pass frequency is for the respective channels. Therefore, Anthem must force you to pick the low pass frequency.
Hope that made sense.

Ed
post #11 of 27
Sorry, ekb, that doesn't make sense. :D The crossover frequency is just that, a number. In the case of bass redirection, the number implies both a high pass and a low pass filter with separate outputs and slope-appropriate knee frequencies. Many pre/pros have channel or channel pair-specific nominal crossover frequencies. Any phase shift is an artifact of the filter implementation, not the crossover frequency. A decent pre/pro will also have channel delay (e.g. distance) and thus phase correction on a per-channel or -channel pair basis. You don't have to specify another (different??) crossover frequency to implement it.

What you describe is a setup where all channels can have *separate* low-pass and high-pass frequencies. That means you're throwing information away. If Anthem has to resort to that instead of per-channel phase correction, I'd hardly term it a "feature".
post #12 of 27
Phase irregularities are an unavoidable consequence of filtering. You can't get around it (except partly with digital filters that would need to buffer for a long time). And this has nothing to do with the channel delays which merely address the fact that sound travels at a finite speed and speakers are at different distances from the listening spot.

I think that you missed a lot in my previous post. I'd suggest re-reading it.

Ed
post #13 of 27
Quote:
Originally posted by ekb
Phase irregularities are an unavoidable consequence of filtering. You can't get around it (except partly with digital filters that would need to buffer for a long time). And this has nothing to do with the channel delays which merely address the fact that sound travels at a finite speed and speakers are at different distances from the listening spot.

I think that you missed a lot in my previous post. I'd suggest re-reading it.

Ed


Are you sure that with DSP you get a phase shift when you change the crossover frequency?

I know that is true of analog filters, but when crossover processing is done in the digital domain is that still true?

--Bill
post #14 of 27
Quote:
Originally posted by DMF


What you describe is a setup where all channels can have *separate* low-pass and high-pass frequencies. That means you're throwing information away. If Anthem has to resort to that instead of per-channel phase correction, I'd hardly term it a "feature".

Lexicon has fancy feature where you can set different crossover frequencies and you do not lose any information.

There are other "high end" units that do this also.

I assume the Anthem is in the "standard" category in which you do lose some information if you do not use the same crossover frequencies for all speakers.

On the other hand, if you sest your surrounds at a higher frequency, there is not that much to lose that you will ever notice. That is my opinion, but I do not listen to music in PL-2 or other multi channel modes. Two channel modes just sound better.on my system. I have "large" mains, so usually I do not (can not) use the subwoofer for music!


Crossover reading material for the newbies!

http://www.hometheaterhifi.com/volum...rs-9-2002.html


--Bill
post #15 of 27
One of my points was that if the processing circuitry can do delay it can also do phase shifting, which is simply a form of delay (you're right, buffer would have to be relatively long - (1/min freq) seconds). But that might not be a valid assumption on my part the way the circuit is designed.

Ed, even if I grant your phase argument it doesn't explain why it's better to throw information away than to have phase collisions when combining the channels. Seems to me the best solution is to do phase correction.

Now, what in your post am I missing?
post #16 of 27
Quote:
Originally posted by spider_bill_2003
Are you sure that with DSP you get a phase shift when you change the crossover frequency?
You probably mean to say when you have a crossover/filter. Not *changing* it.
Quote:
I know that is true of analog filters, but when crossover processing is done in the digital domain is that still true?

--Bill
Yes it's still largely true in the digital domain. The only way to eliminate phase irregularities is to incorporate what is going to happen in the future. In the analog world you can't do that. That's what is meant by causal filters. But in the digital world you can look into the future by buffering your data. So this can lead to improved filters. But you'd have to buffer forever to completely eliminate phase problems.

Ed
post #17 of 27
Quote:
Originally posted by ekb
You probably mean to say when you have a crossover/filter. Not *changing* it.

Ed


Maybe I got lost here, but I thought you were talking about changing the crossovers frequency setting, say 80HZ to 60HZ and getting a phase change.

Are you talking about using a crossover and different frequencies, or are you talking about using a crossover (small speaker setting) verses no crossover (large speaker settings).

Just trying to keep things straight!

--Bill
post #18 of 27
Quote:
Originally posted by DMF
Ed, even if I grant you're phase argument it doesn't explain why it's better to throw information away than to have phase collisions when combining the channels. Seems to me the best solution is to do phase correction.
By throwing away, I assume that you mean having a lower low-pass filter and a higher high-pass filter. Thus introducing a hole in the frequency spectrum. Well the parameters that you choose are your choice. With Anthem, they're giving you a choice. Most other receivers automatically just set the low and high pass turnover frequencies to be the same. Again, the reason Anthem allows you to do this, is because only *ONE* lowpass frequency can be chosen for all small channels. But *MANY* high pass frequencies can be selected for the various small channels. So if you pick different high pass frequencies, then some channels may have a hole, others might overlap, and some might match. You'd think that the solution is to also give the same multiple choices for the low pass - but the combining of the low passed signals would be messed up due to phase irregularities. Largely, you CANNOT correct those phase irregularities. So Anthem feels that potentially introducing holes and overlaps is less damaging than the problems of the combined low pass signal with different filters.

Ed
post #19 of 27
Quote:
Originally posted by spider_bill_2003
Maybe I got lost here, but I thought you were talking about changing the crossovers frequency setting, say 80HZ to 60HZ and getting a phase change.

Are you talking about using a crossover and different frequencies, or are you talking about using a crossover (small speaker setting) verses no crossover (large speaker settings).

Just trying to keep things straight!

--Bill
I'm saying that when you filter - say low pass, the primary thing that you are trying to accomplish is to reduce the level above the selected frequency. But a side effect, is that the phase of the signal is affected in the Xover region. In a bass management system, the low passed signals of all small channels are combined. If they are all low passed at different frequencies, then the phase irregularities of the different channels do not align up. And so you'll get some constructive and some destructive interference at different frequencies. The end result is an irregular bass response.

Ed
post #20 of 27
Okay, then why not have a universal crossover? Not marketable? :D


(And I'm afraid I don't buy the "can't do" phase correction line. You might have to assume a min frequency, but is that so bad? And are you going to argue that every unit with multiple low-pass filters has lousy bass?)
post #21 of 27
Quote:
Originally posted by ekb


In a bass management system, the low passed signals of all small channels are combined. If they are all low passed at different frequencies, then the phase irregularities of the different channels do not align up. And so you'll get some constructive and some destructive interference at different frequencies. The end result is an irregular bass response.

Ed


Well, from a practical point of view, unless all of the redirected bass signals on each channel (as recorded) are identical, you will get constructive and destructive interference anyway when the bass signals are mixed.

However, I get your point. You may as well start out as close as you can to perfection to get consistent results!

--Bill
post #22 of 27
Quote:
Originally posted by DMF
Okay, then why not have a universal crossover? Not marketable? :D


(And I'm afraid I don't buy the "can't do" phase correction line. You might have to assume a min frequency, but is that so bad? And are you going to argue that every unit with multiple low-pass filters has lousy bass?)

I think the anthem has a single low pass setting, but multi high pass settings.

So does my receiver.

I agree with you about speaker distances. If you change the speaker "distance", you do change the timing of the signal. This in effect does change the relative phase with other signals.

I call it a time/phase/distance settings.

My subwoofer distance setting does not match the actual distance from the seating area, but all other speakers do!

--Bill
post #23 of 27
We shouldn't be jumping on Ed about Anthem's design choices. I think he'd agree with us that it's a compromise. Is there some forum where Anthem answers these type of questions?
post #24 of 27
BTW, I'm not an Anthem owner. I always thought that their implementation was a little strange - but maybe their solution is a reasonable one. There is a universal standard - it's called THX and all channels are small and Xover at 80 Hz.

I like the idea of individual crossovers, but I do think that there are some real technical dificulties in implementing them if you want to get it perfect. I think that the saving grace is that the problems with individual crossovers is largely a theoretical one, and in practical implementations, it's difficult to actually hear those problems.

Also, the Anthem bass management has been discussed a lot. Both in the AVS forum and other places.

Ed
post #25 of 27
I'm out!,....;)
>>>--->
post #26 of 27
Maybe the better approach is to ask the vendor of my pre/pro (Outlaw Audio) about the phase issue and how their design deals with. Thanks for the insights, Ed. I'll report back if/when I hear something.
post #27 of 27
I believe that Outlaw uses a Cirrus (brand) processor. HK among others also use these processors. Since the individual Xovers are implemented in the Cirrus chips, all those receivers offer that feature. I'm not sure how much light Outlaw can shed on the matter - but it will be interesting to hear what they say.

Ed
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